As Internet technologies develop rapidly and material and spiritual cultures of people become richer, there are more requirements for video applications on the Internet, and in particular, requirements for high-definition video applications. However, a data volume of a high-definition video is huge, and a problem of compression coding of the high-definition video needs to be first resolved, so that the high-definition video can be transmitted on the bandwidth-limited Internet. Currently, two international organizations: the Motion Picture Experts Group (Motion Picture Experts Group, “MPEG” for short) under the International Organization for Standardization (International Organization for Standardization, “ISO” for short)/International Electrotechnical Commission (International Electrotechnical Commission, “IEC” for short) and the Video Coding Experts Group (Video Coding Experts Group, “VCEG” for short) under the International Telecommunication Union-Telecommunication Standardization Sector (International Telecommunication Union-Telecommunication standardization sector, “ITU-T” for short), are dedicated to developing international video coding standards. Established in 1986, the MPEG is dedicated to developing related standards in the multimedia field, where the standards are mainly applied to storage, broadcast and television, streaming media on the Internet or a wireless network, or the like. The ITU-T mainly develops video coding standards oriented to the real-time video communications field, such as videophone and videoconference applications.
In the past decades, international video coding standards oriented to various applications have been successfully developed, mainly including: the MPEG-1 standard applied to a video compact disc (Video Compact Disc, “VCD” for short), the MPEG-2 standard applied to a digital versatile disc (Digital Video Disc, “DVD” for short) and digital video broadcasting (Digital Video Broadcasting, “DVB” for short), the H.261 standard, H.263 standard, and H.264 standard applied to videoconferencing, the MPEG-4 standard allowing coding of an object in any form, and the latest High Efficiency Video Coding (High Efficiency Video Coding, “HEVC” for short) standard.
In comparison with the latest video coding standard HEVC, for a sequence including rotational or scaling motion, a motion compensation prediction technology based on a linearly changing motion vector field can improve coding efficiency significantly. In a conventional motion compensation prediction technology based on affine transformation, after an affine transformation parameter of a picture block is obtained, a motion vector of each pixel in the picture block needs to be computed, motion compensation prediction is performed according to the motion vector of each pixel, and therefore, a motion compensation prediction signal of each pixel is obtained. Because the motion vector of each pixel in the picture block may vary, different operations need to be performed on the pixels according to the motion vectors. Complexity of pixel-based motion compensation prediction is very high. To reduce coding/decoding complexity, a related technology tries further dividing a picture block into picture subblocks, obtaining a motion vector of each picture subblock, and then obtaining a motion compensation prediction signal of each picture subblock.
However, in the related technology, sizes of the picture subblocks are fixed. If the picture subblocks are excessively small, relatively high coding/decoding complexity is caused. If the picture subblocks are excessively large, coding/decoding efficiency is reduced.